MCQs on Advanced Error Handling | Dart

Master Advanced Error Handling in Dart with 30 insightful MCQs covering topics like custom exceptions, asynchronous error handling, and stack traces for debugging. Test your skills on these essential Dart concepts.

---

MCQs on Advanced Error Handling in Dart

Custom Exceptions

1. What is a custom exception in Dart?
   a) An error that occurs in built-in classes
   b) An exception defined by the user to handle specific errors
   c) A system-generated error
   d) A function that returns an error
2. How do you define a custom exception class in Dart?
   a) By extending the Exception class
   b) By using the try-catch block
   c) By implementing the Error class
   d) By using throw keyword
3. Which of the following is the correct syntax for defining a custom exception in Dart?
   a) class MyException implements Exception {}
   b) class MyError extends Error {}
   c) class MyException extends Error {}
   d) class MyError implements Exception {}
4. How can you throw a custom exception in Dart?
   a) throw new MyException();
   b) throw MyException;
   c) throw new Exception('Error!');
   d) throw MyError();
5. When should you use custom exceptions in Dart?
   a) To handle internal errors only
   b) When a specific error needs more contextual information
   c) For all types of errors
   d) Only for network-related issues
6. What can a custom exception contain in Dart?
   a) Just the error message
   b) Just the error type
   c) Custom information related to the error (e.g., error code)
   d) Nothing, it’s an empty class
7. How can you catch a custom exception in Dart?
   a) By using catch block with the exception type
   b) By using finally block
   c) By using on block with the error type
   d) By catching all errors globally
8. What is the benefit of using custom exceptions?
   a) They are faster than built-in exceptions
   b) They provide more context and improve error handling logic
   c) They are easier to read
   d) They eliminate the need for try-catch blocks
9. Can you define custom exception types based on different scenarios in Dart?
   a) Yes, you can define multiple types of custom exceptions
   b) No, only one custom exception type can be defined
10. What is a best practice when naming a custom exception in Dart?
    a) Use a name that reflects the error scenario
    b) Use the name of the class where the exception occurred
    c) Use generic names like CustomError
    d) Name it after the function throwing the exception

---

Error Handling in Asynchronous Code

11. How do you handle errors in asynchronous functions in Dart?
    a) Using try-catch inside the asynchronous function
    b) Using the await keyword to catch errors
    c) Using the catchError method of Future
    d) Both a and c
12. Which of the following is the correct way to handle errors with Futures in Dart?
    a) future.catchError((e) => print(e));
    b) future.catchError((e) => return e);
    c) future.then((result) => result).catchError((e) => handleError(e));
    d) future.complete(() => print('Done'));
13. What does the catchError method do in Dart’s asynchronous code?
    a) It handles synchronous errors only
    b) It catches and handles errors thrown in asynchronous code
    c) It cancels a Future execution
    d) It pauses the execution of the program
14. In Dart, what will happen if an unhandled error occurs in an asynchronous function?
    a) The error is caught by the try-catch block
    b) The application terminates silently
    c) It causes a runtime exception
    d) The error is passed to the catchError callback
15. How can you propagate errors in asynchronous functions in Dart?
    a) By returning the error in the callback function
    b) By using rethrow keyword
    c) By logging the error and stopping execution
    d) By handling the error within the function itself
16. How do you handle errors in asynchronous stream operations in Dart?
    a) Using await and catchError
    b) Using Stream.catchError() method
    c) By defining onError inside stream.listen()
    d) Both b and c
17. Can you retry an asynchronous operation after an error in Dart?
    a) Yes, using the retry method
    b) Yes, manually invoking the asynchronous function again
    c) No, retrying is not possible
    d) No, it will always fail again
18. Which Dart feature helps handle asynchronous errors in a stream efficiently?
    a) Stream.error()
    b) Stream.onError()
    c) catchError()
    d) Stream.fail()
19. How can asynchronous error handling improve program robustness?
    a) By allowing uninterrupted execution
    b) By preventing error propagation across async boundaries
    c) By suppressing all exceptions
    d) By logging errors only
20. What is the advantage of using await with try-catch for asynchronous error handling?
    a) It simplifies the error-handling code
    b) It executes all errors in parallel
    c) It makes asynchronous functions synchronous
    d) It guarantees no errors occur

---

Stack Traces and Debugging

21. What is a stack trace in Dart?
    a) A list of all functions in the program
    b) A log of where the error occurred and the function call path
    c) A collection of error types
    d) A snapshot of memory during execution
22. How do you access a stack trace in Dart?
    a) By using Error.stackTrace
    b) By using StackTrace.current
    c) By using ErrorDetails
    d) By printing the error message
23. What does a stack trace typically show?
    a) Memory consumption during error occurrence
    b) The sequence of function calls leading to the error
    c) The contents of all local variables
    d) The type of exception thrown
24. What can you do with a stack trace in Dart?
    a) Debug and identify the root cause of errors
    b) Ignore it, as it’s not useful
    c) Use it to optimize code
    d) Use it to measure program execution time
25. What is the purpose of debugging in Dart?
    a) To fix all syntax errors
    b) To inspect code and track issues during execution
    c) To run the code in production environments
    d) To optimize code for better performance
26. Which method can you use to print the stack trace in Dart?
    a) print(stackTrace)
    b) printError(stackTrace)
    c) debugPrint(stackTrace)
    d) logError(stackTrace)
27. What is hot reload in Dart’s debugging process?
    a) A way to restart the application
    b) A method to update code without restarting the application
    c) A method to log errors
    d) A debugging tool for database connections
28. What does a stack trace help you identify during debugging?
    a) The memory usage
    b) The exact location and flow of the error
    c) The state of the program
    d) The variable values during execution
29. What is the main advantage of debugging asynchronous code in Dart?
    a) It helps identify unhandled exceptions in asynchronous operations
    b) It provides faster execution of asynchronous tasks
    c) It ensures asynchronous code works synchronously
    d) It makes asynchronous code easier to maintain
30. How can you improve error handling in production Dart applications?
    a) By removing all stack traces
    b) By logging errors with detailed stack traces and using proper exception handling
    c) By disabling all exception handling in production
    d) By using try-catch without logging

---

Answer Key

Qno	Answer (Option with Text)
1	b) An exception defined by the user to handle specific errors
2	a) By extending the Exception class
3	a) class MyException implements Exception {}
4	a) throw new MyException();
5	b) When a specific error needs more contextual information
6	c) Custom information related to the error (e.g., error code)
7	a) By using catch block with the exception type
8	b) They provide more context and improve error handling logic
9	a) Yes, you can define multiple types of custom exceptions
10	a) Use a name that reflects the error scenario
11	d) Both a and c
12	c) future.then((result) => result).catchError((e) => handleError(e));
13	b) It catches and handles errors thrown in asynchronous code
14	c) It causes a runtime exception
15	b) By using rethrow keyword
16	d) Both b and c
17	b) Yes, manually invoking the asynchronous function again
18	c) catchError()
19	b) By preventing error propagation across async boundaries
20	a) It simplifies the error-handling code
21	b) A log of where the error occurred and the function call path
22	a) By using Error.stackTrace
23	b) The sequence of function calls leading to the error
24	a) Debug and identify the root cause of errors
25	b) To inspect code and track issues during execution
26	a) print(stackTrace)
27	b) A method to update code without restarting the application
28	b) The exact location and flow of the error
29	a) It helps identify unhandled exceptions in asynchronous operations
30	b) By logging errors with detailed stack traces and using proper exception handling